Systems and methods to measure fluid in a body segment

ABSTRACT

The present disclosure introduces systems and methods to measure fluid in a body segment. In one embodiment, a computer system used to measure fluid in a body segment is described. A current generation module may be used to emit an electrical through at least one body segment. The electrical current may be used to measure fluid-volume content of the at least one body segment. An electrode module having a plurality of electrodes may be attached to the current generation module. A signal-processing module may be used to measure changes in the electrical current through at least one body segment. Further, an impedance module may be used to calculate fluid-volume change in at least one body segment and determine the flow of fluid through the at least one body segment. Other embodiments also are described.

BACKGROUND

Impedance plethysmography is a medical test, which measures smallchanges in electrical resistance throughout body segments. Suchmeasurements can be useful in determining fluid volume changes in a bodysegment. Measuring fluid flow through a body segment may be useful inhelping medical professionals determine the presence of existing orpotential health issues in a patient. Importantly, impedanceplethysmography accomplishes this task in a manner that is not invasiveto a patient.

SUMMARY

The present disclosure introduces systems and methods to measure fluidin a body segment. In one embodiment, a computer system used to measurefluid in a body segment is described. A current generation module may beused to emit an electrical through at least one body segment. Theelectrical current may be used to measure fluid-volume content of the atleast one body segment. An electrode module having a plurality ofelectrodes may be attached to the current generation module. Asignal-processing module may be used to measure changes in theelectrical current through at least one body segment. Further, animpedance module may be used to calculate fluid-volume change in atleast one body segment and determine the flow of fluid through the atleast one body segment. Other embodiments are also described.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is set forth with reference to the accompanyingfigures, in which the left-most digit of a reference number identifiesthe figure in which the reference number first appears. The use of thesame reference numbers in different figures indicates similar oridentical items or features.

FIG. 1 is a block diagram illustrating a general overview of a fluidmeasurement system, according to an example embodiment.

FIG. 2 is a block diagram illustrating a set of computer program modulesto enable fluid measurement of a body segment into a computer system,according to an example embodiment.

FIG. 3 is a block diagram illustrating a method to measure fluid in abody segment, according to one embodiment.

FIG. 4 is a diagram illustrating exemplary measurement principles tomeasure fluid flow in a body segment, according to an exampleembodiment.

FIG. 5 is a perspective view of an apparatus to measure blood flow,according to an example embodiment.

FIG. 6 is a block diagram illustrating a fluid measurement system,according to an example embodiment.

DETAILED DESCRIPTION

The following detailed description is divided into several sections. Afirst section presents a system overview. A next section providesmethods of using example embodiments. The following section describesexample implementations. The next section describes the hardware and theoperating environment in conjunction with which embodiments may bepracticed. The final section presents the claims.

System Level Overview

FIG. 1 comprises a block diagram illustrating a general overview of afluid measurement system according to an example embodiment 100.Generally, the fluid measurement system 100 may be used to measure theflow of fluid through a body segment. The fluid measurement system 100is designed to measure blood flow to a body segment in a continuous andnon-invasive manner. For example, system 100 can be used to measure thevolume of blood in the carotid artery noninvasively using bioimpedancein association with the timing of the heartbeat to calculate the volumeof blood that is fed to the brain. In this exemplary implementation, thefluid measurement system 100 comprises inputs 102, computer programprocessing modules 104, and outputs 106.

In one embodiment, the fluid measurement system 100 may be a computersystem such as shown in FIG. 6. Inputs 102 are received by processingmodules 104 and processed into outputs 106. Inputs 102 may include anelectric current, a plurality of electrodes, and a plurality of readingsand calculations.

A first input 102 is an electric current, which may be generated andapplied through at least one body segment of a patient. A patient may beany living being, including humans and animals. The electric current maybe produced by an electrical source. An electrical source may be anydevice or apparatus capable of generating an electric current. Oneexample of an electric source may be a current generator circuit. Inorder to measure the fluid in a body segment continuously, the electriccurrent should be constant. The electric current may be a constantsinusoidal alternating current.

A second input 102 may be a plurality of electrodes. The electriccurrent may run through a plurality of electrodes connected to a bodysegment. In one embodiment, some of the plurality of electrodes may alsobe directly connected to the electrical energy source. In an alternativeembodiment, each of the plurality of electrodes may be connected to theelectrical source. Electrical impedance of the plurality of electrodesmay be measured by applying a constant current through the body segment.Changes in flow of an electrical current through a body segment mayoccur because of changes in fluid-volume content of the body segment. Inan exemplary embodiment, the fluid of a body segment may be blood. Bloodis a conductive electrolyte, and the electrical impedance of a givenbody segment is dependent on the amount of blood within the segment. Asblood enters the body segment, during each cardiac cycle or as a resultof fluid redistribution, its impedance decreases. This change inelectrical impedance may be measured by the plurality of electrodes.

A third input 102 may be a plurality of readings and calculations. Theplurality of readings may be electrical impedance readings includingboth original impedance readings and changes in fluid-volume content ofa body segment. The plurality of calculations may include applyingmathematical equations such as a Nyboer formula to the electricalimpedance readings to determine patient vital signs. Patient vital signsmay physiological statistic taken to assess basic bodily functions. Somecommon patient vital signs may include blood flow to a particular bodysegment and also heart rate. Please refer to the “exampleimplementations” section of this detailed description for additionalreference to the Nyboer formula.

Processing modules 104 generally include routines, computer programs,objects, components, data structures, etc., that perform particularfunctions or implement particular abstract data types. The processingmodules 104 receive inputs 102 and apply the inputs 102 to capture andprocess data producing outputs 106. The processing modules 104 aredescribed in more detail by reference to FIG. 2.

Outputs 106 are produced by receiving the inputs 102 and applyingprocessing modules 104 to the inputs 102. The outputs 106 may include afluid flow reading and a heart rate reading. The fluid flow reading maybe determined by using the plurality of calculations to calculate thefluid-volume change occurring in a body segment and multiplying thatvalue by the heart rate reading. A heart rate reading can be determinedfrom the electrical impedance readings. These outputs 106 may provide anindication of a patient's health status.

FIG. 2 is a block diagram of the processing modules 104 of the systemshown in FIG. 1, according to various embodiments. Processing modules104, for example, comprise a current generation module 202, an electrodemodule 204, a signal-processing module 206, and an impedance calculationmodule 208. Alternative embodiments are also described below.

The first module, a current generation module 202, may be used togenerate an electric current. The generated electric current may beemitted through at least one body segment. The emitted electric currentmay be used to measure a fluid-volume content of the at least one bodysegment over a period of time In one embodiment, the current generatedby the current generation module 202 may be continuous. Providing acontinuous and constant current through a body segment may allowaccurate capturing of changes in the fluid-volume content of the bodysegment. The current generation module may be connected to an electricalsource to generate an electrical current. In an exemplary embodiment, acurrent generator circuit may be used to produce a constant sinusoidalalternating current, which can be applied through a body segment.

The second module, an electrode module 204, may have a plurality ofelectrodes connected to the current generation module 202 to conduct theelectrical current. A plurality of electrodes may be attached to atleast one body segment of a patient. In one embodiment, the plurality ofelectrodes may be attached to multiple body segments of a patient, tomeasure fluid flow more accurately throughout the body of a patient. Anytype of electrode may be used including bare or shielded electrodescomprised of mild steel, high-carbon steel, special alloy steel, castiron, or nonferrous materials, among others.

The third module, a signal-processing module 206, may be used to measurechanges in flow of the electrical current through at least one bodysegment. Changes in the electrical current may occur as the fluid-volumeof a body segment changes. In one embodiment, the signal-processingmodule 206 may use a four (4)-electrode method to determine impedancechanges of the electrical current through a body segment. A constantsinusoidal alternating current may be applied by the circuit generationmodule 202, which may pass longitudinally through a first set ofelectrodes (part of the electrode module 204). Next, a voltage drop ismeasured between a second set of electrodes (part of electrode module204). The change in voltage of the constant sinusoidal alternatingcurrent may be used by the impedance calculation module 208 to calculatea fluid-volume content change in a body segment.

A fourth module, an impedance calculation module 208 may be used tocalculate a fluid flow through a body segment. Determining afluid-volume change in the body segment and applying a Nyboer formulacalculation may do this. Changes in the electrical impedance of a bodysegment may occur as the fluid-volume content changes. Changes inelectrical impedance readings may be recorded and as the fluid-volumecontent changes. In one embodiment, the fluid of a body segment may beblood. As blood enters a body segment, during each cardiac cycle or as aresult of fluid redistribution, its impedance decreases. Thefluid-volume content change may be determined and used in a calculationto determine fluid flow in a body segment by applying a Nyboer formula.Please refer to the “example implementations” section of this detaileddescription for a breakdown of the Nyboer formula.

In an alternative embodiment, an additional processing module 104,namely, a display module 210 may be used to illustrate a representationof the electrical current through the at least one body segment. Thedisplay module 210 may be used to represent electrical impedancereadings and calculations. The display module 210, to visually projectimpedance readings and calculations, may use a monitor or screendisplay. In one example embodiment, the display module 210 mayillustrate numerical values of patient vital signs. In anotherembodiment, the display module 210 may illustrate more complex graphicaland pictorial representations of patient vital signs.

Yet another alternative embodiment, an additional processing module 104,namely, an electrocardiogram (“ECG”) module 212 may be used tosynchronize signal processing and calculation of a heart rate. The ECGmodule 212 may produce an ECG signal, which can measure the activity ofa heart over a period of time The ECG module 212 may detect theR-wave-to-R-wave interval (“RR interval”), which may be used to measureelectric stimulus as it passes through the heart. The RR interval may beused to determine a heart rate reading. A heart rate reading can be usedin the calculation to determine flow of fluid through a body segment.

Exemplary Methods

In this section, particular methods to measure fluid in a body segmentand example embodiments are described by reference to flow charts. Themethods to be performed may constitute computer programs made up ofcomputer-executable instructions.

FIG. 3 is a block diagram illustrating a method to measure fluid in abody segment, according to an example embodiment. The method 300represents one embodiment of a fluid measurement system such as thefluid measurement system 100 described in FIGS. 1 and 6, respectively.The method 300 may be implemented by emitting a constant sinusoidalalternating current through a first set of electrodes attached to atleast one body segment (block 302), measuring a voltage drop between asecond set of electrodes attached to the at least one body segment(block 304), and calculating a fluid-volume change in the at least onebody segment (block 306).

A constant sinusoidal alternating current is emitted through a first setof electrodes at block 302. The constant sinusoidal alternating currentof block 302 may be a constant current of one (1) milliampere (“mA”) andone hundred (100) kilohertz (“kHz”). In an exemplary embodiment, theconstant sinusoidal alternating current of block 302 may passlongitudinally through the first set of electrodes. The first set ofelectrodes of block 302 may be attached to at least one body segment. Inone embodiment, the first set of electrodes may be attached to multiplebody segments. An electrical source may be used to generate the constantsinusoidal alternating current of block 302. One example of an electricsource used to produce an electrical current may be a current generatorcircuit.

At block 304, a voltage drop is measured between a second set ofelectrodes attached to the at least one body segment. Voltage dropbetween electrodes may be measured using a voltmeter or calculated usingOhms law. Calculating a voltage drop between electrodes may be useful indetermining the fluid-volume content change of a body segment.

A fluid volume change in the at least one body segment is calculated atblock 306. The fluid-volume change in the at least one body segment maybe calculated by applying a Nyboer formula. Please refer to the “exampleimplementations” section of this detailed description for a breakdown ofthe Nyboer formula. The fluid volume change may be calculated after theoccurrence of a fluid distribution into a body segment. In oneembodiment, the occurrence of fluid redistribution may occur during acardiac cycle. The determination of fluid-volume change in a bodysegment may be used to measure the fluid flow in a body segment bymultiplying the fluid-volume change amount by the heart rate of apatient.

An alternative embodiment to FIG. 3 further comprises acquiring anelectrocardiogram (block 308). The electrocardiogram of block 308 may beused for R-wave detection between RR intervals to synchronize signalprocessing and calculation of a heart rate. Determining a heart rate maybe useful in measuring the fluid flow in a body segment.

Exemplary Implementations

Various examples of computer systems and methods for embodiments of thepresent disclosure have been described above. Listed and explained beloware alternative embodiments, which may be utilized to measure fluid in abody segment. Specifically, an example embodiment of calculating a fluidchange volume in at least one body segment is explained in thedescription of FIG. 4 below.

FIG. 4 is system illustrating exemplary measurement principles tomeasure fluid flow in a body segment, according to an exampleembodiment. The system 400 represents one embodiment of a fluidmeasurement system such as the fluid measurement system 100 described inFIGS. 1 and 6, respectively. Further, the system 400 of FIG. 4 comprisesa constant current 402 running through a body segment, a plurality ofelectrodes 404 attached to the body segment, and a plurality ofcalculations 406-414 used to determine patient vital signs. Patientvital signs may physiological statistic taken to assess basic bodilyfunctions. A patient may be any living being including humans andanimals. In an exemplary embodiment, the fluid in the body segment maybe blood. The related patient vital signs measured may include rate ofblood flow and heart rate.

A constant current 402 runs through a body segment of a patient. Theconstant current 402 may be generated by an electrical energy source. Anelectrical energy source may be any device or apparatus capable ofgenerating an electric current. An example embodiment of an electricalenergy source may be a current generator circuit. In one embodiment, theconstant current 402 may be a constant sinusoidal alternating current ofone (1) mA and one hundred (100) kHz.

The constant current 402 may pass through a plurality of electrodes 404attached to at least one body segment. In an example embodiment, theconstant current 402 may pass longitudinally though the plurality ofelectrodes 404. In one embodiment, some of the plurality of electrodes404 may be directly connected to the electrical energy source. In analternative embodiment, each of the plurality of electrodes 404 may beconnected to the electrical source. The plurality of electrodes 404 maybe comprised of multiple sets of electrodes attached to various bodysegments. In an exemplary embodiment, the plurality of electrodes 404may have three sets of electrodes. A first set of electrodes may becurrent electrodes. Current electrodes may be directly connected to theelectrical source and used to measure the constant current 402. A secondset of electrodes, voltage electrodes, may be used to measure thevoltage drop between the voltage electrodes placed on various bodysegments. In one embodiment, the voltage electrodes may be placed on theneck and head of a patient to gain electrical impedance readings in theneck and carotid artery of a patient. A third set of electrodes,electrocardiogram (“ECG”) electrodes, may be used to produce anelectrocardiographic reading of the patient. The ECG reading may beuseful in evaluating cardiovascular activity of the heart over a periodof time including determining a heart rate.

A plurality of calculations 406-414 may be used to determine patientvital signs. As previously described, patient vital signs may includeevaluating blood flow to a body segment. One exemplary embodiment of abody segment could be a brain. The system 400 may be used to determineblood flow to the brain. The plurality of calculations 406-414 mayinclude applying the Nyboer formula to calculate fluid volume change ofa body segment. Assuming that you have two body segments with differentcross-sections, the following formula may be applied:

dV=ρL ² /Z ₀ ² d Z

dV=ρL ² /Z ₀ ² d Z

where:

dV=volume change of blood [ml]

p_(b)=specific resistance of blood [Ωcm]

L=distance between the measurement electrodes [cm]

Z₀=basic impedance between the measurement electrodes [Ω]

dZ=impedance change during blood flow through the artery carotid

In measuring blood flow to the brain, the Nyboer formula may be appliedto the neck and carotid artery, assuming that the neck and carotidartery form two paraxial cylinders with different cross-sections.

At block 406, the electrical impedance reading of the voltage electrodesmay be determined. At block 408, the impedance change during blood flowthrough the carotid artery is calculated. Both the electrical impedancereading of the voltage electrodes and the impedance change during bloodflow through the carotid artery may be used in the Nyboer calculation atblock 410. The resulting calculation from block 410 produces the changein fluid volume (in milliliters “mL”) of a body segment. In an exemplaryembodiment, this value may be used to calculate the blood flow to a bodysegment such as the brain.

The ECG electrodes may be read at block 412. A heart rate may bedetermined from the ECG reading at block 414. A blood flow calculation416 representing blood flow to a body segment can be determined bytaking the change in fluid volume of the body segment and multiplyingthat value by the heart rate of the patient.

Exemplary Hardware and Operating Environment

This section provides an overview of one example of hardware and anoperating environment in conjunction with which embodiments of thepresent disclosure may be implemented. In this exemplary implementation,a software program may be launched from a non-transitorycomputer-readable medium in a computer-based system to execute functionsdefined in the software program. Various programming languages may beemployed to create software programs designed to implement and performthe methods disclosed herein. The programs may be structured in anobject-orientated format using an object-oriented language such as Javaor C++. Alternatively, the programs may be structured in aprocedure-orientated format using a procedural language, such asassembly or C. The software components may communicate using a number ofmechanisms well known to those skilled in the art, such as applicationprogram interfaces or inter-process communication techniques, includingremote procedure calls. The teachings of various embodiments are notlimited to any particular programming language or environment. Thus,other embodiments may be realized, as discussed regarding FIGS. 5 and 6below.

FIG. 5 is a perspective view of an apparatus to measure blood flow,according to an example embodiment. The apparatus 500 comprises acurrent generator circuit 502 having a plurality of channels, aplurality of electrodes 504 connected to the current generator circuit502, a processor 506 attached to the current generator circuit 502, anda display unit 508 connected to the processor 506. The apparatus may beused to measure blood flow to a body segment in a continuous andnon-invasive manner.

The current generator circuit 502 may be used to provide a constant andsinusoidal current to the apparatus 500. In one embodiment, a constantand sinusoidal alternating current of 1 mA and 100 kHz may be passedthrough the apparatus 500. Additionally, the current generator circuit502 may have a plurality of channels. The plurality of channels maycommunicate with each other to relay information. In an exampleembodiment, the plurality of channels may include an electricalimpedance channel. The electrical impedance channel may allow for anumber of electrical impedance readings to be detected and registered bythe plurality of electrodes 504 and used in the plurality ofcalculations performed on the processor 506. In another exampleembodiment, the current generator circuit 502 may have an ECG channel.The ECG channel may be used to provide an ECG signal and detect the RRinterval, which may be used to calculate heart rate, and also in acalculation to determine blood flow of at least one body segment.

A plurality of electrodes 504 may be connected to the current generatorcircuit 502. The plurality of electrodes 504 may also be attached to atleast one body segment of a patient. A patient may be any living beingfor which vital signs may be detected, including humans and animals. Theplurality of electrodes 504 may be used to determine a plurality ofelectrical impedance readings by applying a four-electrode method to theplurality of electrodes. In the example 4-electrode method, a constantsinusoidal alternating current is passed longitudinally through a firstset of electrodes (one (1) and two (2)). A voltage drop is measuredbetween a second set of electrodes (three (3) and four (4)). In anexemplary embodiment, the plurality of electrodes 504 may have more thanfour electrodes connected to body segments of the patient including ECGelectrodes to measure an ECG signal used to evaluate a heart rate of apatient.

Electrical impedance measures the opposition to alternating current in acircuit. Measuring electrical impedance may capture relative amplitude,voltages and related phases of the current. Applying a constant currentthrough a body segment may allow the plurality of electrodes 504 tocapture the changes in flow of the electrical current as thefluid-volume content changes. The plurality of electrical impedancereadings may include a blood flow reading and a heart rate reading. Anoriginal electrical impedance reading may be detected by connecting theplurality of electrodes 504 to a body segment.

As the fluid-volume content changes in a body segment, derivativeimpedance may be detected. Both the original electrical impedancereading and the derivative electrical impedance reading may be used inthe calculation of blood flow to a body segment.

A processor 506 may be attached to the current generator circuit 502 tocompute a plurality of calculations. The plurality of calculations mayinclude applying a Nyboer formula to the plurality of electricalimpedance readings to determine blood flow in a body segment. Pleaserefer to the “example implementations” section of the detaileddescription for a breakdown of the Nyboer formula. Other calculationsrelated to patient vital signs may also be included in the plurality ofcalculations.

A display unit 508 may be connected to the processor 506. The displayunit 508 may be used to display numeric values of both the plurality ofelectrical impedance readings and the plurality of calculations. Both ofthese readings may be used to indicate the patient's vital signs.Patient vital signs detected may include blood flow and heart rate. Inone example embodiment, the display unit 508 may numerically illustratethe patient's heart rate and also the calculated blood flow to a bodysegment. In another embodiment, the display unit 508 may illustrate morecomplex graphical and pictorial representations of the patient's vitalsigns. The processor 506 may generate such representations.

An alternative embodiment of the apparatus 500 to measure blood flow mayfurther comprise a plurality of indicators 510 connected to theprocessor 506. The plurality of indicators 510 may be used to indicate ahealth status of a patient. A patient's health status may be determinedfrom the combination of the results of the plurality of electricalimpedance readings and the plurality of calculations. In one exampleembodiment, the plurality of indicators 510 may be color-coded lights tovisibly alert a health professional of the health status of the patient.In one embodiment, the plurality of indicator 510 lights may belight-emitting diodes (“LEDs”). For example, a red LED may be used toindicate that the condition of a patient's health status is dangerousand attention is needed. A yellow LED may be used to indicate that thepatient's health status is heading towards a dangerous condition andshould be monitored. A green LED light may be used to indicate that thepatient's health status is safe. In another embodiment, the plurality ofindicators 510 may be auditory.

FIG. 6 is a block diagram illustrating a fluid measurement system,according to an example embodiment. Such embodiments may comprise acomputer, a memory system, a magnetic or optical disk, some otherstorage device, or any type of electronic device or system. The computersystem 600 may include one or more processor(s) 602 coupled to anon-transitory machine-accessible medium such as memory 604 (e.g., amemory including electrical, optical, or electromagnetic elements). Themedium may contain associated information 606 (e.g. computer programinstructions, data, or both) which when accessed, results in a machine(e.g. the processor(s) 602) performing the activities previouslydescribed herein.

CONCLUSION

This has been a detailed description of some exemplary embodiments ofthe present disclosure contained within the disclosed subject matter.The detailed description refers to the accompanying drawings that form apart hereof and which show by way of illustration, but not oflimitation, some specific embodiments of the present disclosure,including a preferred embodiment. These embodiments are described insufficient detail to enable those of ordinary skill in the art tounderstand and implement the present disclosure. Other embodiments maybe utilized and changes may be made without departing from the scope ofthe present disclosure. Thus, although specific embodiments have beenillustrated and described herein, any arrangement calculated to achievethe same purpose may be substituted for the specific embodiments shown.This disclosure is intended to cover any and all adaptations orvariations of various embodiments. Combinations of the aboveembodiments, and other embodiments not specifically described herein,will be apparent to those of skill in the art upon reviewing the abovedescription.

In the foregoing Detailed Description, various features are groupedtogether in a single embodiment for the purpose of streamlining thedisclosure. This method of disclosure is not to be interpreted asreflecting an intention that the claimed embodiments require morefeatures than are expressly recited in each claim. Rather, as thefollowing claims reflect, the present disclosure lies in less than allfeatures of a single disclosed embodiment. Thus, the following claimsare hereby incorporated into the Detailed Description, with each claimstanding on its own as a separate preferred embodiment. It will bereadily understood to those skilled in the art that various otherchanges in the details, material, and arrangements of the parts andmethod stages which have been described and illustrated in order toexplain the nature of this disclosure may be made without departing fromthe principles and scope as expressed in the subjoined claims.

It is emphasized that the Abstract is provided to comply withrequirements for an Abstract that will allow the reader to quicklyascertain the nature and gist of the technical disclosure. It issubmitted with the understanding that it will not be used to interpretor limit the scope or meaning of the claims.

1. A computer system (104) to measure fluid in a body segmentcomprising: a current generation module (202) emitting an electric anelectrical current through at least one body segment to measure afluid-volume content of the at least one body segment; an electrodemodule (204) having a plurality of electrodes attached to the at leastone body segment; a signal-processing module (206) to measure changes inflow of the electrical current through the at least one body segment asthe fluid-volume of the at least one body segment changes; and animpedance calculation module (208) to calculate a fluid flow through theat least one body segment by determining a fluid-volume change in the atleast one body segment and applying a Nyboer formula.
 2. The computersystem (104) of claim 1, further comprising a display module (210) toillustrate a representation of the electrical current through the atleast one body segment.
 3. The computer system (104) of claim 1, furthercomprising an electrocardiogram module (212) using an electrocardiogramsignal for R-wave detection to synchronize signal processing andcalculation of a heart rate.
 4. The computer system (104) of claim 1,wherein the signal-processing module (206) uses a four-electrode methodto determine impedance change of the electric current through the atleast one body segment.
 5. The computer system (104) of claim 1, whereinthe current generation module (202) further comprises a currentgenerator circuit used to generate a constant sinusoidal alternatingcurrent.
 6. A method (300) to measure fluid in a body segmentcomprising: emitting (block 302) a constant sinusoidal alternatingcurrent through a first set of electrodes attached to at least one bodysegment; measuring (block 304) a voltage drop between a second set ofelectrodes attached to the at least one body segment; and calculating(block 306) a fluid volume change in the at least one body segment byapplying a Nyboer formula after an occurrence of fluid distribution. 7.The method (300) of claim 6, wherein the at least one body segment is aheart.
 8. The method (300) of claim 7, further comprising acquiring(block 308) an electrocardiogram signal and using the electrocardiogramfor R-wave detection to synchronize signal processing and calculation ofa heart rate.
 9. The method (300) of claim 6, wherein emitting (block302) uses a current generator circuit to produce the constant sinusoidalalternating current.
 10. The method (300) of claim 6, wherein theconstant sinusoidal alternating current passes longitudinally throughthe first set of electrodes.
 11. The method (300) of claim 6, whereinthe occurrence of fluid redistribution occurs during a cardiac cycle.12. The method (300) of claim 6, wherein the constant sinusoidalalternating current is one mA and one hundred kHz.
 13. An apparatus(500) to measure blood flow comprising: a current generator circuit(502) having a plurality of channels, wherein the current generatorcircuit provides a constant and sinusoidal current; a plurality ofelectrodes (504) connected to the current generator circuit (502) todetermine a plurality of electrical impedance readings by applying afour-electrode method to the plurality of electrodes (504); a processor(506) attached to the current generator circuit (502) to compute aplurality of calculations, wherein at least one of the plurality ofcalculations includes applying a Nyboer formula to the plurality ofelectrical impedance readings; and a display unit (508) connected to theprocessor (506) to display numeric values of the plurality of electricalimpedance readings and the plurality of calculations.
 14. The apparatus(500) of claim 13, further comprising a plurality of indicators (510)connected to the processor (506) to indicate a status of a patientdetermined from the plurality of electrical impedance readings and theplurality of calculations.
 15. The apparatus (500) of claim 14, whereinthe plurality of indicators (510) are color coordinated.
 16. Theapparatus (500) of claim 13, wherein the plurality of calculationsincludes a blood flow calculation.
 17. The apparatus (500) of claim 13,wherein the plurality of electrical impedance readings includes a bloodflow reading.
 18. The apparatus (500) of claim 13, wherein the pluralityof electrical impedance readings includes a heart rate reading.
 19. Theapparatus (500) of claim 13, wherein the plurality of channels of thecurrent generator circuit (502) includes an electrocardiogram channel.20. The apparatus (500) of claim 13, wherein the plurality of channelsof the current generator circuit (502) includes at least one impedancechannel.